Ultra-small Fe2N nanocrystals embedded into mesoporous nitrogen-doped graphitic carbon spheres as a highly active, stable, and methanol-tolerant electrocatalyst for the oxygen reduction reaction

A low-cost, highly active, stable, and methanol tolerant electrocatalyst towards the oxygen reduction reaction (ORR) is extremely desirable for promoting the commercialization of fuel cells. Herein, we reported a facile two-step pyrolysis and acid leaching process to synthesize a high performance ORR electrocatalyst, where ultra-small Fe2N nanocrystals were incorporated into mesoporous nitrogen-doped graphitic carbon spheres (MNGCS). The Fe2N/MNGCS electrocatalysts with difference Fe2N contents and BET surface areas were obtained via altering the acid leaching time, and all exhibited the apparent electrocatalytic activity. The optimized ORR activity was achieved over (Fe2N/MNGCS)(4) with the positive half-wave potentials (0.881 V vs RHE), high selectivity (4 e(-) process), excellent long-term stability (95.2% of the initial current remaining after 60,000 s of continuous operation) and good tolerance against methanol-crossover effect (94.9% of the current retained prior to 4.0 M methanol injection) in alkaline media, which even was more superior to that of commercial PtiC catalyst. The remarkable ORR activity was originated from the cooperative effect of ultra-small Fe2N nanocrystals and MNGCS, where the balance of catalytic active site density, mesoporous structure, BET specific surface area, and electron conductivity played a key role in determining the ORR performance. (C) 2016 Elsevier Ltd. All rights reserved.